/Engine/Plugins/Animation/ControlRig/Source/ControlRig/Public/Rigs/RigHierarchy.h
Get the current active for the passed in key. This is only valid when only one parent has a weight value and the other parents have zero weights
Returns the first parent with a non-zero weight
[FRigElementKey](API\Plugins\ControlRig\Rigs\FRigElementKey) GetActiveParent ( const [FRigElementKey](API\Plugins\ControlRig\Rigs\FRigElementKey) & InKey ) const